1. Field of the Invention
The present invention relates to a magnetic random access memory (MRAM) using the magnetoresistive effect.
2. Description of the Related Art
Recently, many memories that store information by using new principles have been proposed. One of these memories is a magnetic random access memory using the tunneling magnetoresistive effect. An example is disclosed in Roy Scheuerlein et. al., ISSCC2000 Technical Digest p. 128, “A 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in each Cell”.
The magnetic random access memory stores information “1” and “0” in MTJ (Magnetic Tunnel Junction) elements. These MTJ elements are arranged at the intersections of write word lines and data select lines (bit lines) intersecting each other. Switching elements are connected in series with the MTJ elements.
In this magnetic random access memory as described above, data is written by supplying electric currents to a write word line and data select line, and making the spin directions parallel or antiparallel in an MTJ element by using a magnetic field generated by the electric currents flowing through the two lines. On the other hand, data is read out by forming a current path by turning on a selected switching element, thereby supplying an electric current to only a selected MTJ element and detecting the resistance value of this MTJ element.
Conventionally, letting F (Feature size) and 2F be the short-side size and long-side size, respectively, of the MTJ element, the cell size when a MOSFET is used as the switching element is 12F2. This makes the cell size of the magnetic random access memory larger than those of a DRAM and flash memory.